1. Field of the Invention
The present invention relates to a small-size and high-zoom-ratio zoom lens suitable for a digital still camera, a video camera, and the like. In particular, the present invention relates to a zoom lens that facilitates reducing the size of an image pickup apparatus during a non-photographing state.
2. Description of the Related Art
As a photographic optical system used for an image pickup apparatus, there is required a zoom lens that can provide high zoom ratio, small size in the entire body, and a reduced thickness of a camera (thickness in a longitudinal direction).
In order to realize a reduction in size of a camera, conventionally there is known a retractable zoom lens in which a distance between lens units becomes smaller during a non-photographing state than during a photographing state, so that the lens units are stored in a camera body.
Also, in order to reduce a camera thickness, there is known an optical-path-bending zoom lens in which a reflecting member (reflecting mirror) configured to bend an optical axis of a photographic optical system by 90° is arranged on the optical axis.
Also, there is known a zoom lens that bends an optical path using a reflecting member during a photographing state and stores lens units located on the object side of the reflecting member in a space formed by driving the reflecting member during a non-photographing state. For example, see Japanese Patent Application Laid-Open No. 2007-279541 and U.S. Pat. No. 7,692,869.
A retractable zoom lens including a reflecting member configured to bend an optical path of a photographic optical system can obtain a high zoom ratio and reduce a camera thickness when applied to a camera. However, in order to obtain these effects, it is important to appropriately set a lens configuration of a zoom lens and appropriately set an arrangement of a reflecting member on an optical path and a configuration of lens units in front of and behind the reflecting member. For example, it is important to appropriately set the lens configuration, such as the number of lens units, a refractive power arrangement of each lens unit, and a movement condition of each lens unit during zooming, and it also is important to appropriately set a position when the reflecting member is arranged on the optical path.
In particular, in order to obtain a high zoom ratio and reduce a camera thickness, it is important to appropriately set a refractive power of a variable-magnification lens unit located on the object side of the reflecting member, and to set an amount of movement of a lens unit located on the image side of the reflecting member during zooming. If these configurations are not appropriately set, it is difficult to obtain the above-described effects and image deterioration often occurs. In Japanese Patent Application Laid-Open No. 2007-279541, a reflecting member is arranged between the second lens unit and the third lens unit, when counted from the object side. Also, Japanese Patent Application Laid-Open No. 2007-279541 discusses a zoom lens in which a front lens group located on the object side of the reflecting mirror is stored in an empty space formed when the reflecting mirror rotates during the non-photographing state.
In U.S. Pat. No. 7,692,869, the reflecting mirror is arranged within the second lens unit when counted from the object side, and the second lens unit does not move during zooming. Also, U.S. Pat. No. 7,692,869 discusses a zoom lens in which a lens unit located on the image side of the reflecting member is moved toward the image side during a non-photographing state, so that lens units located the object side are stored in the empty space. In these zoom lenses, refractive power of a lens unit having negative refractive power located on the object side of the reflecting member is weaker than refractive powers of the other lens units.
Therefore, a total effective diameter of a front lens unit is increased, or an amount of movement of a lens unit on the image side of the reflecting member during zooming is increased so as to obtain a desired zoom ratio. Also, a camera width tends to be increased. As a result, it is difficult to achieve a high zoom ratio.